The present invention relates to rotating disk memory assemblies, and more particularly, to carriage structures employed therein.
Rotating disk memories comprise one or more disks driven about a vertical spindle axis. Each disk typically has a plurality of concentric tracks on one or both surfaces from which information is read or onto which information is written by means of reading and/or writing heads. One of the disks generally carries a dedicated servo track which contains head position information and which is read by a dedicated servo head. The servo head provides the input to a servo system which positions the heads over the surface of the disks, generally moving the heads radially with respect to the disks. The heads are carried on arms which are coupled to the voice coil actuator by the carriage. The coil is selectively energized by the servo system to move radially with respect to the disks. The movement of the coil is transferred to the heads through the carriage structure. During track accessing or following, the carriage moves rectilinearly and this rectilinear movement excites resonances in the carriage. When the carriage is excited into a major resonance mode servo control deteriorates. In order to increase the operable frequency band width of the servo, it is therefore necessary to minimize the low frequency resonance modes and thereby increase the frequency of the first major resonance mode.
There has, therefore, been a need for a carriage structure which minimizes low frequency resonance modes and increases the "natural frequency" of the carriage.
One attempt to improve carriage resonance characteristics is shown in U.S. Pat. No. 4,144,466 wherein an elastomeric material is provided between the coil and carriage to dampen vibrations.
Other prior art structures are shown in U.S. Pat. Nos. 4,034,411; 4,001,889; 3,760,206; 3,743,794; 3,740,736; 3,666,977; 3,665,433; 3,614,333; and 850,036.
None of these references show a carriage structure which sufficiently avoids the low frequency resonance problems associated with previous carriages as outlined above.